Doubters of Evolution

[Gonzo]

I pose to you a hypothetical situation.

There are several assumptions which are known as facts that must be taken into account first though.

1) Genetic mutations exist (or at the very least accept that there are large amounts of varying genetics throughout a population). Examples would be varying eye color, hair color, and a variety of others regarding almost every aspect of an organism.

2) These mutations are coded for within DNA and can be passed down to offspring.

3) When mutations are selected for they have can "stacking up" effect to some degree, as we would see with dog breeding. (for example the breeding of bloodhounds with extremely sensitive sense of scent).


Now for my example lets say we take individuals from a human population and select for traits, much like animal breeding. We select for individuals with an extended tail bone/spine and continue to select for them throughout the generations. Based upon the above assumptions you will eventually have a group of individuals with an appendage much like a tail. Now if we select for smaller body size and body hair as well, we have something that looks very much like a monkey, but it wouldn't be and it would most likely still be able to breed with the regular human population. However, if you select for certain traits regarding sexual reproduction, specifically the acidity of the vagina and size of it as well (perhaps even shape). And you have the males in the population selected for characteristics that correspond, it will eventually make sexual reproduction with the normal human population impossible (Which under one definition of the species concept, will make them separate species). There are also some other wild genetic traits that exist in the human population that could be selected for, like webbed digits or blue skin even.


If this example does not convince you I ask that you point out the reasons so that I may use our existing knowledge of genetics and heritability to propose another hypothetical example that may persuade you. I also ask that you lay the groundwork on what constitutes a separate species in your opinion so that my example may incorporate it. Also, if you disagree with my assumptions I can help illustrate them as fact.

I realize my example uses artificial selection rather than natural selection, but I can substitute artificial pressures for environmental ones in the next situation I provide.

[Goose]

I pose to you a hypothetical situation.

Why do you need hypotheticals? Isn't there any real data we can observe?

There are several assumptions which are known as facts that must be taken into account first though.

Right off the bat we have a problem. Any argument that begins by listing it's "assumptions" is not going to be very cogent.

1) Genetic mutations exist (or at the very least accept that there are large amounts of varying genetics throughout a population). Examples would be varying eye color, hair color, and a variety of others regarding almost every aspect of an organism.

OK.

2) These mutations are coded for within DNA and can be passed down to offspring.

OK.

3) When mutations are selected for they have can "stacking up" effect to some degree, as we would see with dog breeding. (for example the breeding of bloodhounds with extremely sensitive sense of scent).

What do you mean by "stacking up"? Please be very specific here.

edit: could please also provide the observed data that supports your idea of "stacking up." Maybe a link or something.

Before I spend a lot of time in this thread can I ask what your definition of "Evolution" is?

[micatala]

There are several assumptions which are known as facts that must be taken into account first though.

Right off the bat we have a problem. Any argument that begins by listing it's "assumptions" is not going to be very cogent.

From a logical standpoint, the only requirement is to have assumptions that are not internally inconsistent. THere is no need to know the assumptions are true to make a 'cogent' or 'logically valid' argument.


I will also note that if any argument which makes assumptions is to be considered not cogent, then most any form of biblical creationism fails miserably. Such arguments are based on innumerable assumptions like:


1) What is written in the Bible, particularly in Genesis, is true.
2) What is written in the Bible is to be taken literally and not metaphorically.

[Goose]

There are several assumptions which are known as facts that must be taken into account first though.

Right off the bat we have a problem. Any argument that begins by listing it's "assumptions" is not going to be very cogent.

From a logical standpoint, the only requirement is to have assumptions that are not internally inconsistent.

That would mean the following argument could be true:
A cannot be both A and ~(A) at the same time in the same sense.
Therefore, A is a number.

THere is no need to know the assumptions are true to make a 'cogent' or 'logically valid' argument.

You can't be serious.

The Cogency and validity of an argument are different things.

Cogency is more a measure of probability or how convincing an argument is.

An argument is said to be valid if it is properly formatted such as Modus Ponens:

If P, then Q
P
Therefore Q.

An argument that begins by telling us assumptions are facts is not very cogent.

[byofrcs]

.....
I realize my example uses artificial selection rather than natural selection, but I can substitute artificial pressures for environmental ones in the next situation I provide.

Seems logical, though I guess with the acid beavers means my saliva is going to have to be a lot more alkaline.


....

Hey, we're monkeys; you asked for it.

[Gonzo]

Before I spend a lot of time in this thread can I ask what your definition of "Evolution" is?

My definition would be a change in organisms over time (generation by generation) due to influences (natural or artificial selection) that affect an organism's ability to reproduce and pass off its genetic material to its offspring. This allows for a population of organisms to diverge from one another physically when subject to different influences over time. The longer the time span of isolation from one another (no gene flow between the populations) compounded with more dissimilar influences increase the amount of divergence we would find.

Why do you need hypotheticals? Isn't there any real data we can observe?

There is in fact real data, we can see the diversification of dogs over a rather short period of time due to artificial influences (a great deal of genetic diversity within the population that has diverged dogs from one another). I pose the hypothetical so that you can see that a great deal of change is feasible based upon evidence of how genetics work.

Right off the bat we have a problem. Any argument that begins by listing it's "assumptions" is not going to be very cogent.

As miticala pointed out, an argument needs assumptions which to be based upon. I can't find sufficient data we can watch in action to support the 3rd premise, so consider it stricken. As for the first 2, You can personally see genetic variation within the human population expressed as the phenotype , which is the physical characteristics genetic information codes for. The second assumption is the basic principle of Heritability .

With the third premise stricken I will adjust the hypothetical situation accordingly.
Again, let's use the human population as an example. Humans differ from each other about .1% genetically. That measly .1 supplies a vast multitude or genetic variance within our population. Let's select for a series of traits within the human population (keep in mind this .1% variance) and see if we could get something you won't call human. Let's select for pointy ears, hairless bodies, blue skin (Methemoglobinemia),blindness, echolocation (check out Ben Underwood), vestigial tail, Pectus excavatum , extra digits on fingers and toes, myostatin increase (resulting in extreme musculature), let's use some genetic traits I possess like semi-dextrous elongated toes (I can peel and eat a banana with my feet), ribs that stick outward (slightly pointed outward at the bottom), and an extremely malleable tongue (can make a clover, flatten then fatten etc.). Let's use pygmy body size as well, and if humans can't mate with pygmies, that just further proves my point. Now we have a creature that no one would identify as human by physical characteristics.

Now we can take it a step further and select for increased acidity of gamete environment (let's say where the sperm meets the egg) and we have sperm that can handle this acidity (increase in neutralizing semen component). Then we select for reproductive organs to become akin to a cloaca (that is to say the male phallus is reduced to a stimulatory sperm hole), and testicles now reside inside the male combined with decreased overall body temperature to accommodate the sperm's requirement for lower temperature. Now we have an organism that isn't a human by physical classifications and can't interbreed with the normal human population.

This is an extreme example that would use artificial selection and still take a great many generations to accomplish the final product. A human population subject to the selective pressures I just explained would provide for an organism classified separately from the normal human population.

[micatala]

There are several assumptions which are known as facts that must be taken into account first though.

Right off the bat we have a problem. Any argument that begins by listing it's "assumptions" is not going to be very cogent.

From a logical standpoint, the only requirement is to have assumptions that are not internally inconsistent.

That would mean the following argument could be true:
A cannot be both A and ~(A) at the same time in the same sense.
Therefore, A is a number.

I was assuming we were at least going to try and make sensible arguments. If you want to deal in non sequiturs then it is somewhat pointless discussion. I didn't think I needed to spell that out.

THere is no need to know the assumptions are true to make a 'cogent' or 'logically valid' argument.

You can't be serious.

The Cogency and validity of an argument are different things.

Cogency is more a measure of probability or how convincing an argument is.

An argument is said to be valid if it is properly formatted such as Modus Ponens:

If P, then Q
P
Therefore Q.

An argument that begins by telling us assumptions are facts is not very cogent.

I agree with your understanding of logically valid. I'll accept that cogent has a different meaning than logically valid.

However, I think we need more discussion on the role of assumptions. I agree assumptions are not necessarily facts and that one should be as clear as possible regarding what is being assumed as a hypothesis and what is being considered factually established.

Ideally, we would make assumptions that are reasonable in the sense that they at least have some probability of being true, the higher the probability the better in most cases. However, I would still hold that an argument based on assumptions that are not necessarily known with certainty to be factual is still an appropriate argument to make, and could even be cogent by your definition.


For example, if we make assumption A and from that assumption can logically deduce conclusions C1, C2, C3, . . . ., Cn and we are able to establish that all the conclusions C1 through Cn are true, then the arguments establishing the logical validity of the conclusions would lead us to reasonably conclude that A may also be true. The more conclusions Ci we have, the higher the probability A is true.

This would not establish A as conclusively true, but would make A a well-supported statement.


Essentially, we can consider each implication A implies Ci as an attempted proof by contradiction of (not A) which failed. If A implies Ci is true ( or logically valid) and Ci is false, then A would have to be false.


Police detectives do this all the time. If they suspect A is guilty, they may reason from this assumption and any know facts to other conclusions. For example, they may be able to establish that if A is guilty, so is B. Now, if B turns out to be innocent, then we know A is innocent also. But, if B is in fact guilty then this strengthens the suspicion that A is also guilty.


Some of the arguments for evolution are certainly of this type. For example, if evolution is true and we find species A with certain characteristics at age 30 Million years ago and we have a species C that has some very similar characteristics but also some changes from A at 20 MYA, we might infer that there was a species B living about 25 MYA showing characteristics transitional between A and C. If we find such a B, this strengthens the case that evolution is true.


Now, if A were false, I suppose it is possible in theory that every valid conclusion that follows from A is true. However, in practice this would be extremely unlikely. I would ask anyone to provide an example of a false statement A from which it is possible to logically derive a large number of diverse conclusions Ci that are all true. And let's stick to statements A and Ci which have at least a modicum of sensibility to them.

[Gonzo]

So everyone agrees that evolution is demonstrable in the example I provided, correct?

[Intrepidman]

.....
I realize my example uses artificial selection rather than natural selection, but I can substitute artificial pressures for environmental ones in the next situation I provide.

Seems logical, though I guess with the acid beavers means my saliva is going to have to be a lot more alkaline.


....

Hey, we're monkeys; you asked for it.

acid beavers, lol.



I was thinking more along these lines...

[Intrepidman]

So everyone agrees that evolution is demonstrable in the example I provided, correct?

No, for 2 reasons

1) I don't accept the initial premise, that genes could be concentrated to produce certain traits without serious consequences. This is what happens when royalty inbreeds:



King Charles II of Spain -- a product of
inbreeding in the Hapsburgh line.

While I don't agree with her assumption of the reason organisms don't inbreed (IE evolution, I think they were designed that way), her conclusions of the effects of inbreeding are sound:

Mammals, most other animals, and higher plants as well, have evolved mechanisms to avoid inbreeding of any sort. Some, like sweet cherries, have even evolved elaborate biochemical mechanism to ensure that their flowers can not be fertilized by themselves or by very genetically similar individuals.

Most pack animals (like lions, primates, and dogs),kick young males out of the pack so as to prevent them from mating with female relatives. Humans have very strong taboos against mating with relatives. Even fruit-flies apparently have a sensing mechanism to avoid too close of inbreeding, even in a closed population they maintain more genetic diversity than they ought to by random mating.

Why do living things avoid inbreeding? Because in general, it is quite bad for a population or an organism to be very inbred. There is a well studied, although only partially understood phenomenon called inbreeding depression.

Inbreeding depression is thought to be caused primarily by the collection of a multitude of deleterious mutations, few in themselves fatal, but all diminishing fitness. Normally, in an outbreeding population these alleles would be selected against, hidden, or corrected by the presence of good alleles (versions of genes) in the population.

We generally think that mutations arise only once in a great while. That is certainly true for individual genes and specific kinds of mutations. However scientists have measured mutation rates in humans, chimpanzees and gorillas and discovered that there are roughly 4.2 mutations/individual/generation that affect the actual final proteins encoded by the genes. (A, Eyre-Walker, P. D. Keightly, Nature 397:344-347. 1999). Of these mutations about 1.5 are deleterious, in other words would cause harm to the animal if they were homozygous. The scientists who performed this analysis suspect that their numbers are actually artificially low for a variety of valid reasons, and estimate that the actual number may be closer to 3 deleterious mutations per individual per generation.

So how come we don't all have tons of genetic diseases? The answer to that is fairly simple, sexual reproduction, and the shuffling of alleles of genes that occurs when two unrelated individuals mate.

When that shuffling can't happen because both parents already have mostly the same alleles, the result will be inbreeding depression, if not in a given litter, then in a few more generations of such breedings.

Inbreeding depression encompasses a wide variety of physical and health defects. Any given inbred animal generally has several, but not all, of these defects. These defects include:

Elevated incidence of recessive genetic diseases

Reduced fertility both in litter size and in sperm viability

Increased congenital defects such as cryptorchidism, heart defects, cleft palates.

Fluctuating assymetry (such as crooked faces, or uneven eye placement and size).

Lower birthweight

Higher neonatal mortality

Slower growth rate

Smaller adult size, and

Loss of immune system function.

http://cc.ysu.edu/~helorime/inbred.html

To me this seems also to be a pretty strong argument against microbe-to-man evolution as well. Since organisms seem to be fighting pretty hard to keep the gene pool mixed and stable.

On to reason 2

2) If your premise were true it would be difficult to say at what point an organism were no longer human. Some in the past put that point at being Jewish. To me even if two 'people' cannot sexually reproduce with each other does not make either one of them not human.

Any more than the inability of Chihuahuas and Great Dane's inablitiy to sexually reproduce with each other stop them from being both dogs.